Compression Opinion

[mopar346]

As I discussed in other threads, I am building a motor for my son's truck. I have been told a few diffent answer to the final compression and was wondering what the collective views are here. It is a 93(ish) 350 4 bolt roller block with forged flat top speed pro pistons and a 64 cc head. Neither the block or the head has had any significant decking in the past.

Thanks in advance, Kevin

[BlackoutSteve]

Have a look at the cam you're selecting and it should have a minimum recomendation.
I'd go at least 10:1

[mopar346]

I believe it is in the 10s and that is what the cam is calling for, I was just curious if anyone knew what it would be with the above combo.

[Mark]

Got any valve relief cuts in the pistons?  If so  and theirs 4 of them then it should be about 9.3 to 1 if not about 9.7 to one assuming a zero deck height.  I've got 1/8" knuckles on my pistons and I'm only pulling about 10.7 to 1.

[mopar346]

Thank you, I believe they have 4 reliefs, I will have them in hand this week end.

[Boston14]

Here's the calculator I use, works great.  http://www.csgnetwork.com/compcalc.html  hope this helps.

boston14

[mopar346]

Thanks, found one at Summit as well, 64 cc heads, with 4 vavle reliefs (+6.1 cc according to summit info sheet), .010 in the hole, .053 compressed gasket, it shows 9.7:1. At 0 deck height it is 10:1. They remaining uncertain is deck height, which I cant measure till the week end.

Thanks folks!

[mopar346]

Checked piston heigth today, .015 in the hole, giving it 9.6:1 compression as long as the head gasket compressed thickness is .053 as I think. The thickness number came from an internet search, does anyone know for sure? It is a regular good quality Fel Pro blue gasket.

[Boston14]

What number Felpro head gasket?   They range from 0.015" to 0.071" thick and have bore diameters from 4.080" to 4.250", giving you a compressed volume anywhere from 3.2cc to 16.1cc. Quite a range and effect on compression!

boston14

[mopar346]

Any way to tell which is which, not that it matters at this point I'm not gonna change anything. Just curious thats all.

[Boston14]

The numbers are stamped into the gaskets.

[mopar346]

Thank you, part number or compressed number?

[BlackoutSteve]

Possibly both, but definitely the part number.

[mopar346]

Steve,

Thanks, I was reading a little of you post down under. You're pretty creative and talented. Great job on creating a unique piece.

[BlackoutSteve]

Thanks for the compliment.. It helps to be single and a little compulsive!
The stuff I have done is pretty easy. I found that out the hard way -by just having a go before deciding to pay someone.
Thanks Kevin.